Abstract: The development of techniques and technologies for the deposition of ultrathin superconducting films, the creation of superconducting structures on a nanometer scale is the basis of significant progress in the field of superconducting receiving systems. Ultrathin NbN films are the basis for a wide range of record-breaking hot electron devices: direct and heterodyne terahertz detectors. Terahertz receivers are especially in demand in high-resolution spectroscopy for astronomical, atmospheric, and medical research. HEB receivers are widely used in terahertz radio astronomy. For example, the Dutch SRON Institute is preparing a project for the GUSTO hot air balloon telescope with a HEB mixer array at 1.4 THz and 1.9 THz. A 5-meter Chinese terahertz telescope DATE5 with HEB mixers at 1.4 THz is installed at the South Pole. The Stratospheric Observatory (SOFIA) uses HEB mixer matrices in the GREAT instrument operating in the 1.2 – 4.7 THz range. It is planned to implement the international project Origins Space Telescope (OST) in the far infrared region based on HEB receivers. The Japanese project Smiles-2 will allow measurements at 1.8 THz in the upper layers of the stratosphere and mesosphere. The development of the Millimetron space observatory continues in Russia.

Abstract: Water content in the cornea may affect the outcome of its excimer laser ablation, especially in presbyopic patients with myopic refraction. This hypothesis can be tested by scanning the cornea in the terahertz (THz) range to determine its hydration level.
Purpose: To study the effect of hydration of the cornea determined by non-contact THz scanning and its biomechanical parameters on the results of photorefractive keratectomy (PRK) in an experiment.
Material and methods: PRK was performed using the Nidek EC-5000 QUEST excimer laser on 8 rabbit eyes. Corneal hydration was evaluated by determining the reflection coefficient (RC) in the THz electromagnetic radiation range before PRK, after 3-5 days, and after 1, 2, 3, and 4 months. Clinical examination included autorefractometry, assessment of corneal thickness and other anatomical and optical parameters of the anterior eye segment (Galilei G6, Ziemer Ophthalmic Systems AG 6.0.2, Switzerland), measurement of corneal hysteresis (CH) and corneal resistance factor (CRF) using the Ocular Response Analyzer (ORA; Reichert, USA), as well as tear production (Schirmer test).
Results: The initial water content in the cornea has a significant effect on the thickness of the removed layer, i.e. on the PRK effect, with correlation coefficient of Rs= -0.976 (p<0.01). The correlation between CH and the ablation depth is less pronounced (Rs=0.643), and CRF had no correlation with it (Rs= -0.089). Biomechanical indicators of the cornea depend on its hydration: changes in CH and CRF after excimer laser ablation qualitatively coincide with changes in RC, the correlation coefficient between RC and the initial value of CH is R= -0.619 (moderate negative correlation).
Conclusion: THz scanning is an effective non-contact technology for monitoring corneal hydration level. The mismatch of the hypoeffect of keratorefractive excimer laser intervention planned for patients with presbyopia with the actual outcome can be caused by individual decrease in the initial water content in the cornea.

Abstract: In this article, present the first detailed study of cascade switching in superconducting photon number resolving detectors. The detectors were made in the form of four parallel nanowires, coupled with the single-mode optical fiber and mounted into a closed-cycle refrigerator with a temperature of 2.1 K. We found out the value of additional false pulses (N cas.sw. ) appearing due to cascade switching and showed that it is possible to set up the detector bias current that corresponds to a high level of the detection efficiency and a low level of N cas.sw. simultaneously. We reached the detection efficiency of 60% and N cas.sw. = 0.3%.